Hi,
I know of no reason why ajaxcontroltoolkit tabs would not work, maybe it does not show up because you have not the needed css.
What I do know is that neither ajaxcontroltoolkit tabs nor jquery tabs are meant to cause postback when the user clicks a tab, They are designed to be client side, the content of all tabs is all loaded into the page when it first renders and tabs are only to organize the content visually. The toolkit tabs have a server event that will fire indicating a tab change, but this would only fire when some other control causes the postback.
You can wire up client side javascript using either the toolkit tabs or jquery, but if you use jqueryui tabs then you should not use our automatic tabs based on the css class name mojo-tabs, because it does not give you a reference to the javascript tabs object, so instead you would have to wire it up yourself using javascript which would allow you to wire up events on it.
PageMethods cannot work inside a usercontrol, they only work inside a page.
You can style mojoGridView by adding the css from the style.config file of your skin, there are several themes to choose from as you can see by looking at style.config in skins that ship with mojoPortal:
<file cssvpath="/Data/style/gridview/SoftGreyGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
<!--
<file cssvpath="/Data/style/gridview/ChromeBlackGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
<file cssvpath="/Data/style/gridview/ChromeGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
<file cssvpath="/Data/style/gridview/GlassBlackGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
<file cssvpath="/Data/style/gridview/SoftGreyGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
<file cssvpath="/Data/style/gridview/WhiteChromeGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
<file cssvpath="/Data/style/gridview/YahooGridView.css" imagebasevpath="/Data/style/gridview/">none</file>
-->
Hope it helps,
Joe